5.3 Overview of Available Functionals

5.3.7 Semi-Empirical Functionals

(June 30, 2021)

The following semi-empirical methods are available in Q-Chem:

  • HF-3c: It is an HF-based semi-empirical method which is used with a minimal basis called MINIX. All the elements from H to Xe are supported. For the elements from Rb (Z = 37) to Xe (Z = 54), def2-ECP has to be used. 1068 Sure R., Grimme S.
    J. Comput. Chem.
    (2013), 34, pp. 1672.
    Link

  • PBEh-3c: It is a DFT based method which is used with def2-mSVP basis set.This is available for all the elements from H to Rn. For the elements from Rb (Z = 37) to Rn (Z = 86), def2-ECP has to be used. It is a more accurate method than HF-3c as it has correlation. 384 Grimme S. et al.
    J. Chem. Phys.
    (2015), 143, pp. 054107.
    Link

Example 5.4  Q-Chem input for HF-3c method.

$molecule
   0 1
   O  -1.551007  -0.114520   0.000000
   H  -1.934259   0.762503   0.000000
   H  -0.599677   0.040712   0.000000
   O   1.350625   0.111469   0.000000
   H   1.680398  -0.373741  -0.758561
   H   1.680398  -0.373741   0.758561
$end

$rem
   SCF_CONVERGENCE   8
   BASIS             MINIX
   METHOD            HF3C
   SCF_GUESS         SAD
$end

View output

Example 5.5  Q-Chem input for PBEh-3c method.

$molecule
   0 1
   O  -1.551007  -0.114520   0.000000
   H  -1.934259   0.762503   0.000000
   H  -0.599677   0.040712   0.000000
   O   1.350625   0.111469   0.000000
   H   1.680398  -0.373741  -0.758561
   H   1.680398  -0.373741   0.758561
$end

$rem
   METHOD           PBEh-3c
   BASIS            def2-mSVP
   XC_GRID          000099000590
   INCDFT           0
   INCFOCK          0
   SCF_CONVERGENCE  8
   THRESH           14
   SYMMETRY         false
   SYM_IGNORE       true
$end

View output